1. Field
This disclosure relates to the technical field of the manufacture of mould pieces by laser sintering of metal powders, in which objects, and more particularly mould pieces, are produced by selectively melting the powders and constructed by superposition of layers. This sintering technique is also referred to as laser sintering or SLM (Selective Laser Melting).
2. Description of Related Art
The advantage of this technique of manufacturing pieces is that the shape of the piece can be computer-modelled and the piece can be manufactured easily by sintering on the basis of this model. Specifically, the laser can be driven by a computer comprising a model of the piece, and the piece can then be manufactured by successively sintering superposed powder layers.
This technique is particularly suitable for the production of complex mould pieces because it makes it possible to manufacture moulding elements of small dimensions, such as lamellae or beadings, in the same operation.
The production of the pieces is carried out on the basis of a horizontal reference plate, on which a first metal powder layer is deposited and is selectively melted with the aid of the light beam coming from the laser source. A second metal powder layer is subsequently introduced, and then the selective melting is continued, and so on until the final piece is obtained.
The reference plate, the surface of which is planar, therefore serves as a base for constructing the object in successive layers. It is therefore not surprising to find that melting the first layer has the effect of welding the plate to the object to be produced, when the metal powder and the metal forming the reference plate have sufficiently close melting points. At the end of the operation, the reference plate then needs to be detached from the final piece, which may either be used as it is or be subjected to a finishing operation. This operation may, for example, be carried out by rapid cutting with the aid of a wire.
There remains a need in the art to exploit this feature and provide a modification of the reference plates and the manufacturing method.
Specifically, it has been found that certain pieces intended to produce curing moulds for tyres can be divided into two separate parts. A first part of the piece can undergo rapid and economical manufacture with the aid of conventional machining means, by moulding or by removing metal, such as by milling, turning or grinding, and does not have a shape which is particularly difficult to produce with the aid of these means.
The second part of the piece, however, has particular shapes which it is expedient to produce with the aid of a laser sintering device of the type above, although its cycle times are generally longer and more expensive to carry out than conventional machining devices. Thus, it is quite often the entire piece which is produced by laser sintering when the piece comprises parts which it would not be possible to produce in another way.